Use of tapes in the pipe corrosion protection industry.
One of the most common uses for tapes in the pipeline industry is to use them to wrap around steel pipes and protect the pipe surface from corrosion. This type of anti corrosion system can be used on large diameter and small diameter pipes alike, although generally different types of tape will be used for each category.
The large diameter pipes tend to use the thicker and more robust bitumen based tapes or the three ply plastic butyl combination tapes.
The smaller diameter pipes tend to use more flexible tape materials which will include PVC adhesive tapes, petrolatum cloth tapes, butyl backed vinyl tapes and cloth tapes.
Large pipeline contracts involving long pipelines usually have their anti corrosion protection applied in the pipe factory leaving their ends uncoated. The joins are then coated with a join sealing tape on site and after the pipe is in place and joined to the pipeline.
Types of anti-corrosion tapes.
The anti-corrosion tape industry is constantly evolving, but broadly speaking these are the existing categories of anti-corrosion tapes available in South Africa today.
Bitumen based anti-corrosion tapes
Bitumen based tapes are typically a layer of tacky black bitumen on a thick plastic backing, usually polyethylene. Most often there is a silicon release liner between the layers of the tape to protect the sticky bitumen from adhering to the back of the previous layer’s plastic.
These tapes tend to be used on the larger diameter pipes and along straight sections of piping. The thick plastic backing provides good mechanical protection from rocks and stones in the back fill of buried pipes. The bitumen layer is thick and allows good adhesion to the pipe surface, even when the surface is not absolutely smooth. Usually a primer is applied to the tape surface before applying this type of tape.
A slightly different version of this a bitumen saturated cloth tape which is applied to the pipe using a blow torch. The use of this product is quite rare these days due the difficulty and danger of applying the tape to the pipe.
Petrolatum pipe wrapping tapes
When it comes to small diameter pipes and piping with lots of bends and tees, the petrolatum cloth tape is a useful solution for corrosion protection. It is a cloth tape impregnated or saturated with a petroleum based grease or wax. The end result is a light brown waxy tape that is flexible and conformable around turns and irregular shapes on a piping system.
Although a little messy to work with because of the wax and grease, it is very easy to apply requiring no special skills or equipment. It is simple to use on smaller pipe diameters because the cloth material allows it to be conformable and easy to maneuver in confined work areas.
The tape is spirally wrapped around the pipe and the tacky nature of the grease holds it in place around the pipe. There is no adhesive so re-positioning of an incorrectly applied tape spiral is easy to do and similarly it is easy to unwind and rework an incorrectly applied section of tape wrapping. These tapes are best applied on site as their lack of adhesive causes problems with shifting tape when the pipe is transported and handled.
This type of anti corrosion tape is used extensively to protect copper pipes from corrosion in the plumbing industry, on fire sprinkler piping systems, and on the piping systems of chemical and industrial plants.
Petrolatum tapes are often using in conjunction with mastic (putty) to cover pipe joins such as couplings, flanges and valves on buried pipes.
PVC pipe wrapping tapes
PVC tapes are also occasionally used for the corrosion protection of pipes, but they have limited acceptance and use in South Africa. This tape is a thicker version of the common electrical insulation tape and is spirally wrapped around the pipe length with each new layer overlapping the previous layer by anything from a few millimetres to 55% of the width of the tape. This latter specification results in an effective double layer of tape protecting the pipe surface.
Butyl based pipe wrapping tapes
The butyl tapes are similar to the bitumen tapes but tend to have a thicker layer of tacky butyl rubber with a thinner plastic backing which tends to be a bit more flexible than most of the bitumen tapes.
These butyl tapes have found a bit of a niche in the pipeline industry by being the preferred product to use on the welded joins of long pipelines. Usually these larger pipes are coated with a plastic or epoxy product in factory, with the ends of each length of pipe left exposed so that welding can be done. Once welded together to form the pipeline, the joins can be wrapped using the butyl tape product on site.